Occurred to me today that the old secular narrative that sees the Dark Ages as a reversal of progress and culture is false -- and an example of selection bias. Proponents are able to maintain the story by focusing on the decline of the Italian peninsula, rather than noticing that the capitol of Roman empire and European culture had simply moved -- to Constantinople.
Emperor Constantine (the first Christian emperor) moved the capitol of the Roman empire to Constantinople (previously Byzantium, today Istanbul). So a Christian Emperor never ruled in Rome. Constantine moved the capitol because Rome was just no good -- it was isolated, and subject to flooding and Malaria. So when we think of Christian Rome, we mustn't think of it as centered in the city of Rome -- because it never was.
The Roman Empire of Constantine (which "scholars" call the Byzantine Empire) was never called the Byzantine Emperor by anyone who lived there. In fact, no city named Byzantium existed under this "Byzantine Empire." Its residents called their empire the Empire of the Romans.
So, no longer the Capital of the Empire, the city of Rome declined and ultimately fell in 410. But that was insignificant. The Capitol of Christian Rome, Constantinople, stood untoppled until the 13th Century. And while Rome was in ruins, the new capitol of the Roman Empire was thriving, economically. Classical science was retained and expanded upon. Justinian made huge legal and political reforms. The magnificent Hagia Sophia was built.
Then, Plague decimated the population in the 500s, and the Muslims seized the moment to attack -- Muslims, incidentally, who were advancing mathematics and science to previously unknown heights.
The story is not one of "Christianity took over and culture stopped." That fiction is maintained only by ignoring that fact that the Capitol of Rome and the center of European civilization moved from one city to another.
The story is very clearly one of "The center of culture -- Christian culture -- and the Roman empire -- moved from the Italian Peninsula to Constantinople."